Hydraulic control assembly

ABSTRACT

A hydraulic control assembly especially suited for operation of a fail-safe valve. An integral structure is provided having a pair of check valves disposed in passageways extending from one chamber of a piston operator to a hydraulic reservoir and the other chamber of the piston reservoir, and in a fluid line extending from a high pressure source. In a fail-safe valve, cavity pressure normally acts on the valve stem and provides the force which moves the valve to its close position. A spring is disposed in the second chamber of the piston operator and, in conjunction with any force resulting from internal cavity pressure on the valve stem, aids in closing the valve. The second chamber is equal or greater in volume than the first chamber so that all of the hydraulic fluid displaced from the first chamber during valve closing can flow into the second chamber. In this way, the hydraulic power needed to pump hydraulic fluid back to the reservoir is not effected by installed hydraulic system variations. Additionally, these results are achieved while containing the fluid in a closed system. Fail-safe valves can be designed to either fail to the open or fail to the closed position.

BACKGROUND AND SUMMARY OF THE INVENTION

Fluidic operators are normally provided for the operation of fail-safevalves in well head assemblies. Since it is necessary to quickly closesuch valves upon command or when a particular well head condition issensed, generally pneumatic operators are provided for the valves, theair in the operator cylinder being exhausted directly into theatmosphere upon closing of the fail-safe valve. This exahaustion of airinto the atmosphere provides a rapid closing time due to a minimum backpressure and not having to recycle the air. Under many circumstances,however, hydraulic actuators are more desirable than pneumaticactuators. Additionally, it is sometimes desirable to effect actuationof the operators with a gaseous fluid that is noxious (i.e., H₂ S), andshould not be vented to atmosphere. Under such circumstances, uponclosing of the fail-safe valve, the fluid must be returned to the fluidreservoir.

In the case of the use of hydraulic fluid for actuation, the necessityfor recycle of the hydraulic fluid results in longer closing time orlarger lines or both, often times making hydraulic actuation infeasible.There have been proposals for the rapid closing of valves with hydraulicactuators, such as shown in U.S. Pat. No. 3,495,501, however suchproposals do not necessarily result in the desired closing quickness,and often require a large number of complicated arrangements includingtwo sources of high pressure hydraulic fluid, a check valve and threeother valves, each valve being a three-way or more valve, etc.

According to the present invention, an actuator is provided, especiallysuited for rapid closing of a fail-safe valve, which is relativelysimple yet provides for rapid valve closing and recycle of the actuatingfluid. [While the invention will be described with particular referenceto hydraulic fluid, it is to be noted that other fluids besideshydraulic fluids may be utilized, and the invention is not to be limitedto hydraulic fluids.] According to the present invention, a pistonactuator is provided disposed in the cylinder and dividing the cylinderinto first and second chambers, the piston movable in a first directionto shrink the first chamber and effect rapid valve closing, and movablein a second direction to shrink the second chamber for opening with thevalve. Biasing means are disposed in the second chamber for biasing thepiston operator for rapid closing, and the first and second chambers areconstructed so that the maximum displaceable volume of the firstcylinder chamber is equal to or less than the maximum displaceablevolume of the second cylinder chamber. During closing of the valve, thefluid displaced from the first piston chamber is vented to the secondpiston chamber rather than being pumped back the distance to thehydraulic reservoir, so that the minimum resistance to piston movementis provided. During the application of high pressure hydraulic fluid tothe first chamber to open the valve, the fluid in the second chamber isthen ultimately pumped back to the reservoir.

An integral valve assembly is provided for valving fluid to the firstand second chambers from and to a high pressure source of hydraulicfluid and a hydraulic reservoir. The integral valve assembly includes afirst passageway in the block leading from a first opening to theexterior of the block to a second opening to the exterior, a first checkvalve disposed in the first passageway for allowing passage of fluidfrom the first opening to the second opening but not vice-versa, asecond passageway in the block leading from a third opening to theexterior of the block to the first check valve operator to bias theoperator closed to prevent passage of fluid through the first passagewaypast the check valve in either direction, a third passageway in theblock leading from the third opening to the second opening, a secondcheck valve disposed in the third passageway for allowing passage offluid from the third opening to the second opening but not vice-versa,and a fourth passageway in the block leading from the second opening toa fourth opening to the exterior of the block. A plurality of valveassemblies may be stacked one upon the other for providing operation ofa plurality of fail-safe valves, common fluid supply and fluid drainlines being provided for the assemblies. According to the invention,only two simple check valves need be provided for effecting the valvingoperations for rapid closing of a fail-safe valve and for openingthereof.

It is the primary object of the present invention to provide hydraulicoperator means capable of rapid movement in one direction, utilizing aminimum number of simple components. This and other objects of theinvention will become clear from an inspection of the detaileddescription of the invention and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary assembly according to thepresent invention with the piston operator in valve open position;

FIG. 2 is a schematic similar to that of FIG. 1 but showing the pistonoperator in valve closed position;

FIG. 3 is a side view of the integral valve assembly of FIG. 1;

FIG. 4 is another side view of the valve assembly of FIG. 1;

FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 4; and

FIG. 6 is a cross-sectional view taken along lines 6--6 of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a fail-safe valve operator assembly, includingthe particular piston and cylinder assembly therefor and the integralvalve assembly therefor. A conventional well head fail-safe valve isshown schematically at 10 in FIGS. 1 and 2. A piston and cylinderassembly 12 is provided as means for opening and closing the fail-safevalve 10, the piston and cylinder assembly comprising a piston 14disposed in a cylinder 15 and separating the cylinder into a firstchamber 16 and a second chamber 17. The first chamber 16 shrinks uponmovement of the piston 14 in a first direction C, and the second chamber17 shrinks upon movement of the piston 14 in a second direction O. Meansare provided for moving the piston 14 in the first and second directionsC, O, such means comprising means 18 for biasing the piston in the firstdirection C for rapid movement of the piston 14 in direction C, andhydraulic means 18'. The hydraulic means 18' includes means defining thepiston cylinder 15 so that the maximum displaceable volume of the firstcylinder chamber 16, which is exhausted during movement of the piston indirection C to effect valve closing, is equal to or less than the volumeof the second cylinder chamber 17, which is exhausted during movement ofthe piston in the second direction O to effect valve opening. This maybe accomplished as shown in FIGS. 1 and 2 by providing interior means18, 19 and 20, the interior means 20 in the first chamber 16 operativelyassociated with piston 14 having a volume greater than or equal to thevolume of the interior means 18, 19 in the second chamber 17 operativelyassociated with piston 14. The biasing means 18 preferably comprises acoil spring that is disposed within the second chamber 17, and interiormeans 19 and 20 comprise a pair of piston rods. As an inspection ofFIGS. 1 and 2 makes clear, the piston rod 20 in the first chamber 16 hasa cross-sectional area, and therefore a volume per unit length, greaterthan that of the piston rod 19 which is connected to the valve 10, thevolume of the rod 20 in an intermediate position of the piston 14exactly between valve opening and valve closing positions being greaterthan or equal to the combined volumes of the coil spring 18 and thepiston rod 19 within chamber 17. By constructing the cylinder 15 in thismanner, the entire contents of the first chamber 16 may be vented to thesecond chamber 17 upon movement of the piston 14 in direction C.

The hydraulic means 18' also comprises a high pressure source ofhydraulic fluid 22 such as a hydraulic pump, a hydraulic fluid reservoir25, and means 26 for valving the hydraulic fluid to effect movement ofthe piston in direction C upon termination of the flow of hydraulicfluid from the high pressure source 22, without leakage of hydraulicfluid from the assembly, and to effect movement of the piston in thesecond direction O responsive to the high pressure fluid from source 22.A master control valve 23 may be provided, which valve can be manuallyoperated and/or condition-responsive to either allow the passage offluid from high pressure source 22 to the first chamber 16, or forventing the high pressure fluid back to the reservoir 25. The valve 23,source 22 and reservoir 25 may be located remote from the cylinder 15,however it is preferred that the valving means 26 be located adjacentthe cylinder 15.

Valving of the hydraulic fluid to effect piston 14 movement is providedby the valving means 26 associated with a plurality of passagewaysinterconnecting the valves and the chambers 16, 17 with the source 22and reservoir 25. A number of fluid lines are provided including a fluidline 30 which leads from source 22 to a first check valve 27 to bias thecheck valve 27 closed when fluid is supplied through line 30. A branch31 off of line 30 is provided leading to a second check valve 29 andfrom second check valve 29 a line 32 extends to a line 33 whichultimately passes to the first chamber 16. The second check valve 29allows fluid flow from line 31 to line 32 (when high pressure fluid isprovided by source 22) but does not allow the passage of fluid from line32 to line 31 (when fluid under pressure is no longer supplied by source22). During operation of the assembly to effect opening of the fail-safevalve 10, the source 22 supplies fluid under pressure through line 30 tobias first check valve 27 closed, the fluid then flowing through line31-- past second check valve 29--through line 32, and ultimately to line33 to first chamber 16 to move the piston 14 in direction O.

A branch line 34 is provided off of line 33, the first check valve 27being provided in branch 34, and a line 35 extending from the firstcheck valve 27. The first check valve 27 allows the flow of fluid fromline 34 to line 35, but does not allow the flow of fluid from line 35 toline 34. When high pressure fluid is supplied to line 30, however, thecheck valve 27 does not allow the passage of fluid from line 34 to 35 ineither direction. The line 35 passes to a line 37 which at one endextends to the second cylinder chamber 17, and at the other end connectsup to a drain line 38 which extends to the hydraulic reservoir 25. Whenfluid is supplied by source 22 through line 30, the fluid vented fromthe second chamber 17 passes through line 37 to line 38, and ultimatelyto the reservoir 25, the power from the pressurized hydraulic fluidbeing supplied to first chamber 16 providing the force for pumping thefluid from second chamber 17 back to the reservoir 25.

Preferably, the valving means 26 and associated lines are provided as anintegral valve assembly 40, which assembly is shown schematically inFIGS. 1 and 2 and shown in more detail in FIGS. 3 through 6. Such anassembly 40 comprises a block of any suitable material having a firstopening 41, a second opening 42, a third opening 43, and a fourthopening 44 therein extending to the exterior of the block. The lines 30through 35, 37 and 38 may be considered to define four passageways inthe block, a first passageway being defined by lines 33, 34, 35, and 37connecting first opening 41 to second opening 42, the first check valve27 being disposed in the first passageway for allowing passage of fluidfrom the first opening 41 to the second opening 42 but not vice versa.The first check valve 27--as shown most clearly in FIG. 5--includes avalve operator 46 which comprises a piston which is spring biased bycoil spring 47 or the like to a closed position, a fluid receivingchamber 48--connected to line 30--being provided. When fluid underpressure is passed into chamber 48, it works with the spring force ofspring 47 to hold the piston operator 46 in the closed position so thatconical head 49 of operator 46 seals against a passageway peripheralseal 50 for the line 34. Once fluid under pressure is removed from thechamber 48, the operator 46 is free to move against the bias of spring47 to allow the passage of fluid between head 49 and passagewayperiphery 50 into line 35.

The second passageway disposed in the block is defined by the line 30,extending from the third opening 43 to the first check valve 27 operator46 to bias the operator closed and prevent passage of fluid through thefirst passageway through the check valve 27 in either direction. Thethird passageway formed in the block is defined by portions of lines 30,31, 32 and 33, the third passageway leading from the third opening 43 tothe first opening 41, the second check valve 29 being disposed in thethird passageway for allowing passage of fluid from the third opening 43to the first opening 41 but not vice versa. The second check valve 29,which is shown most clearly in FIG. 5, comprises a conventional checkvalve having a spring 51 biasing a sealing head portion 52 thereof intosealing engagement with the periphery 53 of line 31, a plurality ofopenings 54 being provided in the head 52 to allow the flow of fluidfrom line 31 to line 32 upon movement of the head 52 against the bias ofspring 51 in response to fluid pressure in line 31. The fourthpassageway formed in the block is defined by lines 37 and 38, the fourthpassageway leading from the second opening 42 to the fourth opening 44.

When it is desired to provide for operation of a plurality of piston andcylinder operators 12 for a plurality of valves 10, a plurality ofblocks (see 40' in FIG. 1) may be provided which are substantiallyidentical to the integral valve assembly 40. The drain line 38 of all ofthe assemblies 40 is common, the connection therebetween being providedmerely by removing plug 55 (see FIG. 6) in drain line 38 of valveassembly 40 and connecting it up to the corresponding line 38 in anothervalve assembly (40'). The openings 43 of each valve assembly (40, 40')are commonly connected to a single source 22, and a separatecondition-responsive valve may be disposed adjacent each opening 43 toprovide selective valving by each of the assemblies 40, 40' to operatetheir respective piston and cylinder arrangements 12.

It will be noted that the assemblies 40, 40' are normally locateddirectly adjacent piston and cylinder arrangements 12, while thehydraulic reservoir 25 and source 22 are located remote from theassemblies 12 at a convenient central location. The first passageway,defined by lines 33, 34, 35 and 37, which leads from the first chamber16 to the second chamber 17 thus has a relatively short length, and hasless fluid resistance than the passageway leading from chamber 16 tohydraulic reservoir 25. This, combined with the relative volumes of thechambers 16, 17, means that upon movement of piston 14 in direction Cunder the influence of spring 18, fluid in chamber 16 will normally flow(see FIG. 2) to the second chamber 17, although flow to line 38 andreservoir 25 is allowed. Thus, the power needed to exhaust the fluidfrom chamber 16 is much less reduced than were it necessary to pump allof the fluid back to reservoir 25, and therefore the spring 18 can bemade smaller, or faster operation of the valve 10 can be provided. Thespent fluid is not pumped back to the reservoir 25 until fluid underpressure is again supplied by source 22 through line 30 to move piston14 in direction O, whereby the fluid from chamber 17 passes through line37 to line 38 and ultimately to reservoir 25.

The structure according to the present invention having been described,an exemplary method of operation thereof will now be set forth:

The fail-safe valve 10 is maintained in open condition by supplyingfluid from high pressure source 22 through valve 23 to line 30, the highpressure fluid in line 30 passing into chamber 48 and biasing the pistonoperator 46 of first check valve 27 closed so that no fluid can passfrom line 34 to line 35, the fluid from line 30 also passing throughline 31, through second check valve 29, through lines 32 and 33 intofirst cylinder chamber 16 to slowly move the piston in direction O,effecting opening of the valve 10. The power supplied by the fluid underpressure pumps the fluid out of second chamber 17 into line 37 to drainline 38, and ultimately to reservoir 25. Movement of the piston 14 indirection O is shown schematically in FIG. 1; the valve 10 will remainopen as long as the line 30 is pressurized.

Should it be desired to close fail-safe valve 10, it will be necessarythat rapid closing be effected. This is accomplished by releasing thehigh pressure from line 30, as by operation of valve 23 to vent thehydraulic fluid to reservoir 25 (the operation of valve 23 beingeffected manually and/or in response to a condition sensed in the wellhead assembly). When this takes place, as shown in FIG. 2, fluid is nolonger prevented from flowing through first check valve 27 from line 34to line 35, and the spring 18 is no longer compressed, the spring 18rapidly moving the piston 14 in direction C. The fluid from firstchamber 16 passes through line 33, 34, 35, and 37 to the second chamber17, the first and second chambers 16, 17 being located relatively closetogether so that a minimum amount of force need be applied by the spring18 to effect such pumping, a flow passageway also being provided throughline 38 to reservoir 25. No fluid can flow through second check valve 29since the check valve 29 will be biased closed. Since the maximumdisplaceable volume of chamber 16 is less than or equal to the maximumdisplaceable volume of chamber 17, essentially all of the fluid fromchamber 16 may be pumped to chamber 17, and rapid closing of the valve10 while retaining the hydraulic fluid in a closed system is thuseffected.

It will be seen that according to the present invention an assembly hasbeen provided that allows rapid closing of a fail-safe valve withhydraulic fluid, yet provides a minimum number of component parts andretains all of the hydraulic fluid within the system. Many of thecomplicated components of prior art proposals, such as shown in U.S.Pat. No. 3,495,501, are eliminated without consequent loss of theirfunction. While the invention has been herein shown and described inwhat is presently conceived to be the most practical and preferredembodiment thereof, it will be apparent to one of ordinary skill in theart that many modifications thereof are possible. For instance, thepiston and cylinder arrangement 12, and the valve assembly 40 need notnecessarily be provided for operation of a fail-safe valve 10, but maybe provided for operation of other structures. Thus, the disclosure ofthe invention is to be considered only as exemplary, and the inventionis to be limited only be the appended claims which are to be interpretedbroadly so as to encompass all equivalent structures and assemblies.

What is claimed is:
 1. A fail-safe valve operator assembly comprising(a)a fail-safe valve, (b) means for opening and closing said fail safevalve, comprising a piston movable in a cylinder and dividing thecylinder into first and second chambers, said piston operativelyconnected to said valve, said piston when moved in a first directionclosing said valve, and when moved in a second direction opening saidvalve, said first chamber having a maximum displaceable volume which isexhausted during movement of said piston in said first direction toeffect valve closing, and said second chamber having a maximumdisplaceable volume which is exhausted during movement of said piston insaid second direction to effect valve opening, (c) means for moving saidpiston in said first and second directions, said means comprising (i)means for biasing said piston in said first direction for rapid movementin said first direction comprising a coil spring disposed in said secondchamber abutting said piston, and (ii) fluid means, and (d) said fluidmeans comprising (i) means defining said piston cylinder so that themaximum displaceable volume of the first cylinder chamber, which isexhausted during movement of said piston in said first direction toeffect valve closing, is equal to or less than the maximum displaceablevolume of the second cylinder chamber which is exhausted during movementof said piston in said second direction to effect valve opening, (ii) ahigh-pressure source of fluid for supplying fluid to said cylinder tomove said piston in said second direction, (iii) a fluid reservoir, and(iv) means for valving said fluid to effect movement of said piston insaid first direction upon termination of the flow of fluid from saidhigh-pressure source without leakage of fluid from the assembly, and toeffect movement of said piston in said second direction responsive tosaid high-pressure fluid source.
 2. An assembly as recited in claim 1wherein said fluid means further comprises means defining a firstpassageway and a passageway leading from said first cylinder chamber tosaid reservoir, said first passageway extending from said first cylinderchamber to said second cylinder chamber, said passageway having ashorter length and less fluid resistance than said passageway leadingfrom said first cylinder chamber to said reservoir.
 3. An assembly asrecited in claim 2 wherein said means for valving said fluid comprisesan integral unit including said first passageway, said first passagewayhaving a first check valve disposed therein for allowing passage offluid therethrough from said first chamber to said second chamber butpreventing passage of fluid, from said second chamber to said firstchamber, said check valve having a check valve operator and a secondpassageway leading from said high-pressure source for supplying fluid tosaid first check valve operator to bias said operator closed to preventpassage of fluid from said first chamber to said second chamber whenfluid under pressure is being provided by said source of fluid underpressure.
 4. An assembly as recited in claim 3 wherein said integralunit further comprises a third passageway leading from saidhigh-pressure fluid source to said first chamber and a second checkvalve disposed in said third passageway for preventing passage of fluidin said third passageway from said first chamber to said second chamberwhile allowing passage of fluid in said third passageway from saidhigh-pressure source to said first chamber.
 5. An assembly as recited inclaim 4 further comprising a fourth passageway leading from said secondchamber to said fluid reservoir.
 6. An assembly as recited in claim 1wherein said means defining said piston cylinder so that the volume ofsaid first chamber is equal to or less than the volume of said secondchamber comprises a first piston rod disposed in said first chamber, anda second piston rod disposed in said second chamber and operativelyconnected to said fail-safe valve, said first piston rod having a largeror equal volume for a given length of said first chamber than the volumeof said second piston rod for the same given length plus the volume ofsaid coil spring in said second chamber.
 7. In a fail-safe valveoperator assembly comprising(a) a fail-safe valve; (b) means for openingand closing said fail-safe valve, comprising a piston movable in acylinder and dividing the cylinder into first and second chambers, saidpiston operatively connected to said valve, said piston when moved in afirst direction closing said valve, and when moved in a second directionopening said valve, said first chamber having a maximum displaceablevolume which is exhausted during movement of said piston in said firstdirection to effect valve closing, and said second chamber having amaximum displaceable volume which is exhausted during movement of saidpiston in said second direction to effect valve opening; (c) means formoving said piston in said first and second directions, said meansincluding (i) means for biasing said piston in said first direction forrapid movement in said first direction, and (ii) fluid means; (d) saidfluid means comprising (i) means defining said piston cylinder so thatthe maximum displaceable volume of the first cylinder chamber is equalto or less than the maximum displaceable volume of the second cylinderchamber, (ii) a high pressure source of fluid for supplying fluid tosaid cylinder to move said piston in said second direction, (iii) afluid reservoir, and (iv) means for valving said fluid to effectmovement of said piston in said first direction upon termination of theflow of fluid from said high-pressure source without leakage of fluidfrom the assembly, and to effect movement of said piston in said seconddirection responsive to said high-pressure fluid source; and wherein (e)said means defining said piston cylinder so that the volume of saidfirst chamber is equal to or less than the volume of said second chambercomprises a first piston rod disposed in said first chamber, and asecond piston rod disposed in said second chamber and operativelyconnected to said fail-safe valve, said first piston rod having a largeror equal volume for a given length of said first chamber than the volumeof said second piston rod for the same given length plus the volume ofany other interior structures in said second chamber.
 8. In a fail-safevalve operator assembly comprising(a) a fail-safe valve; (b) means foropening and closing said fail-safe valve, comprising a piston movable ina cylinder and dividing the cylinder into first and second chambers,said piston operatively connected to said valve, said piston when movedin a first direction closing said valve, and when moved in a seconddirection opening said valve, said first chamber having a maximumdisplaceable volume which is exhausted during movement of said piston insaid first direction to effect valve closing, and said second chamberhaving a maximum displaceable volume which is exhausted during movementof said piston in said second direction to effect valve opening; (c)means for moving said piston in said first and second directions, saidmeans including (i) means for biasing said piston in said firstdirection for rapid movement in said first direction, and (ii) fluidmeans; (d) said fluid means comprising (i) means defining said pistoncylinder so that the maximum displaceable volume of the first cylinderchamber is equal to or less than the maximum displaceable volume of thesecond cylinder chamber, (ii) a high pressure source of fluid forsupplying fluid to said cylinder to move said piston in said seconddirection, (iii) a fluid reservoir, and (iv) means for valving saidfluid to effect movement of said piston in said first direction upontermination of the flow of fluid from said high-pressure source withoutleakage of fluid from the assembly, and to effect movement of saidpiston in said second direction responsive to said high-pressure fluidsource; and wherein (e) said fluid means further comprises an integralunit including a first passageway extending from said first cylinderchamber to said second cylinder chamber, said first passageway having afirst check valve disposed therein for allowing passage of fluidtherethrough from said first chamber to said second chamber bypreventing passage of fluid from said second chamber to said firstchamber, said check valve having a check valve operator and a secondpassageway leading from said high-pressure source for supplying fluid tosaid first check valve operator to bias that operator closed to preventpassage of fluid from first said chamber to said second chamber whilefluid under pressure is being provided by said source of fluid underpressure, and a third passageway leading from said high pressure fluidsource to said first chamber in a second check valve disposed on saidthird passageway for preventing passage of fluid in said thirdpassageway from said high-pressure source to said first chamber.
 9. Inan assembly as recited in claim 8 further comprising a fourth passagewayleading from said second chamber to said fluid reservoir.
 10. In anassembly as recited in claim 8 wherein said biasing means comprisesspring means disposed in said maximum displaceable portion of saidsecond chamber and in operative engagement with said piston.